This invention relates to multipurpose film cassettes of the type in which a photographic film strip is exposed, processed and projected without removal from the cassette and, more particularly, it concerns a novel arrangement for indicating the processed or unprocessed condition of the film strip within such a cassette.
U.S. Pat. No. 3,641,896, issued to Rogers B. Downey, et al., on Feb. 15, 1972; and U.S. Pat. Nos. 3,778,140 and 3,800,306, issued respectively on Dec. 11, 1973 and Mar. 26, 1974, to Edwin H. Land, contain exemplary disclosures of a motion picture system by which a supply of light sensitive film contained in a multipurpose cassette can be exposed in a camera adapted to receive the cassette and then processed or developed to provide the conventional series of positive transparent image frames by placing the cassette in a viewing apparatus capable of activating a processor also contained in the cassette. Thus, once the film strip has been exposed, the image sequence recorded thereon may be viewed by projection after a time interval only as long as that required to rewind the film strip, the processing operation being performed on the film during this initial rewind.
Of the many components required for satisfactory operation of such systems, the film cassette and the processor contained therein are perhaps most critical. For example, the development of transparent image frames on the light sensitive emulsion of the film strip after exposure in the camera of the system requires the deposit of processing fluid on the film strip. This is accomplished by expressing processing fluid through an orifice to a moving run of the film strip during the processing cycle. After the processing fluid is released upon initiation of the processing cycle, it must be deposited uniformly across the width of the emulsion as well as uniformly along the full useful length of the film strip with a high measure of reliability inasmuch as any non-uniformity or discontinuity in the layer of processing fluid deposited on the film strip will result in undesirable blemishes plainly observable in the images to be viewed. When the processing operation has been completed, any excess processing fluid within the cassette must be secured against leakage to the overall cassette interior. Finally, provision is made in the cassette for indicating whether the film strip has been processed or not inasmuch as the operating mode of the viewing apparatus in which the cassette is inserted after exposure is different for a cassette containing an exposed unprocessed film strip than it is for a cassette containing an exposed and processed film strip. Exemplary disclosures of such a motion picture film system having means for indicating the processed or unprocessed condition of the film strip within such a cassette are shown in the above-cited U.S. Pat. No. 3,778,140 as well as U.S. Pat. No. 3,785,725, issued to J. F. Batter, Jr., et al, on Jan. 15, 1974, and U.S. Pat. No. 4,003,064, to P. B. Mason, issued on Jan. 11, 1977.
In a typical system, the multipurpose film cassette is provided with a processed/unprocessed indicating means in the form of an internal electrical connection between two external electrical contacts which are accessible from the outside of the cassette housing. The internal electrical connection between the contacts is broken when the film is first rewound back onto the supply reel during processing. The existence of an electrical continuity between the two contacts indicates an unprocessed film, while an electrical discontinuity between the contacts indicates a processed film. The viewer/processor into which the cassette is inserted is provided with a control system which includes an operating cycle selector which is responsive to the cassette film condition indicating means to condition the control system for either a processed-film operating cycle or an unprocessed-film operating cycle.
Typically, a valve member, which is slidably mounted within the cassette and which is displaceable upon completion of processing to disable the film processing means, is used to form the internal electrical connection mentioned above. The valve member comprises a metallic portion which is movable, responsive to film advancement in a given direction following processing, from a first position wherein it provides the desired electrical interconnection to a second position wherein the valve member serves to disable the cassette-contained processor and wherein it no longer serves to provide an electrical connection between the two contacts. In most prior art arrangements, the electrical contact between the slidably mounted valve and the contacts contained within the cassette has been achieved as a result of a contact force resulting from an inherent resiliency in the two contacts and wherein the slidably mounted valve has been held downwardly against this inherent resiliency to establish the positive contact.
In addition to the functional importance of the cassette-contained components in the operation of the system, the cassette is preferably a package for both the supply of film and the processing fluid from the point of manufacture to use by the consumer. The cassette also serves as a permanent container for the exposed and processed film strip during storage and subsequent projection cycles. In this respect, therefore, the processing components contained in the cassette can be considered as disposable in light of their being used only once with each cassette manufactured. This aspect of the cassette adds a still further requirement; that is, that the processing components as well as other cassette components be inexpensive and capable of mass production without detracting from operational performance in effecting the processing operation. Although the cassette structure illustrated in the above-mentioned U.S. patents, as well as other patents and pending applications commonly owned by the assignee of the present invention, have evidenced significant success from the standpoint of achieving system objectives, there is a need for simplification and corresponding cost reduction in the cassette components which it is desirable to be capable of making by mass production manufacturing techniques. Further in order to reduce production costs, it is desirable to minimize the number of components in a cassette as well as to simplify the assembly process.